1. Field of the Invention
The present invention relates to a cooling system for an information device, and more specifically a cooling system for preventing an information device used in a data center, a server room, etc., from thermally running out of control due to overheating.
2. Description of the Related Art
Conventionally, a number of servers as information devices are placed in e.g. a company's server room, a data center where an information device such as a computer is used to perform data calculation, data summarization, etc. In a room where a server is used, an air-conditioning device keeps the room temperature at a certain fixed value in order to prevent the server from thermally running out of control due to overheating. For a conventional server-cooling system using an air-conditioning device, a method of cooling an entire room thereby to cool a server placed in the room has been adopted.
On the other hand, in recent years, a space-saving compact server, which is termed a blade type server, is becoming more common. A blade type server consists of a set of about ten slim boards (blades) mounted in a box-type case and each board has a function comparable to that of a server for personal computers. The enclosures of such blade type servers are stacked in a rack having a height of about 2 meters. In a data center and the like, a number of such racks are arrayed in positions in an air-conditioned room.
A conventional method of cooling racks in an air-conditioned room is as follows: preparing a number of rows of racks each composed of racks arrayed in positions in a lateral direction; and blowing cooling air, which flows under the floor from an air conditioner positioned near a wall of the room, into cooling aisles formed between the rack rows, thereby to cool the rack rows, which is then warmed and returned to the air conditioner through warm air passages.
However, such blade type servers are large in processing power, and therefore consume a large amount of electric power and generate a large amount of heat. In cases where the amount of heat generated by servers is not so large, a conventional cooling system which cools a whole room can be used to lead cooling air to cooling aisles and cool each server. However, in cases where the density of heat generated by servers is larger, the temperature of the servers cannot be lowered only by cooling air, which is supplied from an air conditioner positioned near a wall of the room, from under the floor to cooling aisles, and hot spots occur at unexpected places. Hence, a conventional cooling system which cools a whole room has not been able to cool a device with a high heat generation density.
Therefore, another cooling system has been used, which includes: covering a whole rack with a housing; providing a blower fan and a cooling coil in the housing; and circulating cooling air in the housing thereby cooling a server case. The cooling system is advertised in a brochure by APC Japan Inc.
However, in the case where cooling air is circulated in a housing has been used, a duct area for circulating cooling air or the like is required for each rack, and a high-speed air flow needs to be used for cooling a heat source with a high heat generation density. The size of the duct areas is large, which poses a problem that the number of racks which can be placed in an air-conditioned room is reduced.